<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
<script>
const arr = [1,2,3,4,5,6];
const arr3 = arr.concat([]);
arr3[0] = 0;
console.log(arr, arr3);
// 重新申请一块空间 开销大
const arr2 = JSON.parse(JSON.stringify(arr));// 引用式拷贝
arr2[0] = 0;
console.log(arr, arr2);
</script>  
</body>
</html>